Transport/Magnetotransport of High-Performance Graphene Transistors on Organic Molecule-Functionalized Substrates

Chen, Shao Yu; Ho, Po Hsun; Shiue, Ren Jye; Chen, Chun-Wei; Wang, Wei Hua

doi:10.1021/nl204036d

Cited by 64 publications

(71 citation statements)

References 40 publications

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“…20 We then employed resist-free fabrication with a shadow mask to reduce possible polymer residue. A crucial step in this process was to control the metal diffusion of electrodes by deliberately increasing the gap between the shadow mask and graphene samples.…”

Section: Introductionmentioning

confidence: 99%

“…Before the transport/magnetotransport measurement, the samples were annealed at 383 K for 3 hours in a low vacuum (Helium atmosphere) to remove adsorbates. 20 We note the critical role of the Ti layer in determining the transport behavior by comparing the two-terminal conductance vs. gate voltage ( − ) curves of a graphene pn-p junction (sample A) and a control sample (sample B), as shown in Figure 1c and 1d, respectively. For sample A, a large field effect is observed for < 7 V, showing a typical graphene characteristic, in which the − curve can be well described by the selfconsistent Boltzmann equation = ( + 0 ) −1 + , where , , and 0 are densityindependent mobility, the resistivity due to short-range scattering, and residual conductance at the Dirac point, respectively.…”

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confidence: 99%

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Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphenep−n−pjunctions

et al. 2016

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We report distinctive magnetotransport properties of a graphene p-n-p junction prepared by controlled diffusion of metallic contacts. In most cases, materials deposited on a graphene surface introduce substantial carrier scattering, which greatly reduces the high mobility of intrinsic graphene. However, we show that an oxide layer only weakly perturbs the carrier transport, which enables fabrication of a high-quality graphene p-n-p junction through a one-step and resist-free method. The measured conductance-gate voltage ( − ) curves can be well described by a metal contact model, which confirms the charge density depinning due to the oxide layer. The graphene p-n-p junction samples exhibit pronounced quantum Hall effect, a well-defined transition point of the zeroth Landau level (LL), and scaling behavior. The scaling exponent obtained from the evolution of the zeroth LL width as a function of temperature exhibits a relatively low value of κ = 0.21 ± 0.01.Moreover, we calculate the energy level for the LLs based on the distribution of plateauplateau transition points, further validating the assignment of the LL index of the QH plateau-plateau transition. KeywordsGraphene p-n-p junction, quantum Hall effect, plateau-plateau transition, scaling behavior, while that of the zeroth LL is temperature (T) independent. 13 In a Corbino geometry, FWHM Δν of the zeroth LL is T dependent and shows scaling behavior with κ = 0.16, which is attributed to an inhomogeneous charge carrier distribution. 19 However, until now, a well-defined QH plateau-plateau transition point of the zeroth LL of graphene has not been directly observed, obscuring a detailed understanding of the scaling behavior of this unique LL. Moreover, the variation of the T exponent in previous reports suggests the need for further investigation of the scaling behavior of the zeroth LL using different methods for the device structures.In this report, we fabricate a high-quality graphene p-n-p junction, achieved via controlled diffusion of metallic contacts, to explore the QH plateau-plateau transition and 4 scaling behavior of graphene. Interestingly, we observe a well-defined transition point corresponding to the zeroth LL, revealing the scaling behavior and a reduced T exponent.There are additional advantages of utilizing a graphene p-n-p junction to explore the transition region of the QHE. First, the presence of the transition between an integer QH plateau and a QH plateau with a fractional value enables direct access to the transition of the zeroth LL. Second, in a graphene p-n-p geometry, the intrinsic graphene is adjoined by the doped graphene from both sides. The doped graphene regions can be viewed as an ideal contact, facilitating the investigation of the transition region of the intrinsic graphene.Moreover, we derive the value of energy level for the observed LLs, which agrees with the theoretical values, further validating the assignment of the LL index of the QH plateauplateau transition.A detailed device fabrication process can be found i...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%

Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphenep−n−pjunctions

et al. 2016

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“…Nevertheless, the level of doping was smaller than that observed for graphene devices on unprocessed SiO 2 /Si substrates. 17 In addition, samples with low levels of residual doping (V C N P close to zero) exhibited higher mobility. This trend is consistent with mobility degradation due to charge-impurity scattering.…”

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confidence: 99%

“…Monolayer graphene was mechanically exfoliated from graphite flakes onto octadecyltrichlorosilane (OTS)-functionalized SiO 2 /Si substrates 17 and examined by optical microscopy and Raman spectroscopy. 18 We utilized e-beam lithography to design the electrode pattern, which matched the specific shape and size of each graphene flake.…”

mentioning

confidence: 99%

“…[19][20][21] The SiO 2 /Si substrates were functionalized with an OTS self-assembled monolayer (SAM) to ensure the enhanced transport properties of graphene. 17 Because the surface of the OTS SAM is hydrophobic, achieving the adhesion of any subsequently deposited layers, such as e-beam resist, is difficult. Therefore, the stencil-mask approach becomes essential and valuable in defining electrode patterns on the OTS-functionalized substrates.…”

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Residue-free fabrication of high-performance graphene devices by patterned PMMA stencil mask

et al. 2014

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Two-dimensional (2D) atomic crystals and their hybrid structures have recently attracted much attention due to their potential applications. The fabrication of metallic contacts or nanostructures on 2D materials is very common and generally achieved by performing electron-beam (e-beam) lithography. However, e-beam lithography is not applicable in certain situations, e.g., cases in which the e-beam resist does not adhere to the substrates or the intrinsic properties of the 2D materials are greatly altered and degraded. Here, we present a residue-free approach for fabricating high-performance graphene devices by patterning a thin film of e-beam resist as a stencil mask. This technique can be generally applied to substrates with varying surface conditions, while causing negligible residues on graphene. The technique also preserves the design flexibility offered by e-beam lithography and therefore allows us to fabricate multi-probe metallic contacts. The graphene field-effect transistors fabricated by this method exhibit smooth surfaces, high mobility, and distinct magnetotransport properties, confirming the advantages and versatility of the presented residue-free technique for the fabrication of devices composed of 2D materials.

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Graphene: An Emerging Electronic Material

et al. 2012

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Graphene, a single layer of carbon atoms in a honeycomb lattice, offers a number of fundamentally superior qualities that make it a promising material for a wide range of applications, particularly in electronic devices. Its unique form factor and exceptional physical properties have the potential to enable an entirely new generation of technologies beyond the limits of conventional materials. The extraordinarily high carrier mobility and saturation velocity can enable a fast switching speed for radio-frequency analog circuits. Unadulterated graphene is a semi-metal, incapable of a true off-state, which typically precludes its applications in digital logic electronics without bandgap engineering. The versatility of graphene-based devices goes beyond conventional transistor circuits and includes flexible and transparent electronics, optoelectronics, sensors, electromechanical systems, and energy technologies. Many challenges remain before this relatively new material becomes commercially viable, but laboratory prototypes have already shown the numerous advantages and novel functionality that graphene provides.

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Transport/Magnetotransport of High-Performance Graphene Transistors on Organic Molecule-Functionalized Substrates

Cited by 64 publications

References 40 publications

Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphenep−n−pjunctions

Observation of quantum Hall plateau-plateau transition and scaling behavior of the zeroth Landau level in graphenep−n−pjunctions

Residue-free fabrication of high-performance graphene devices by patterned PMMA stencil mask

Graphene: An Emerging Electronic Material

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